///
// * jdbm LICENSE v1.00
// *
// * Redistribution and use of this software and associated documentation
// * ("Software"), with or without modification, are permitted provided
// * that the following conditions are met:
// *
// * 1. Redistributions of source code must retain copyright
// *    statements and notices.  Redistributions must also contain a
// *    copy of this document.
// *
// * 2. Redistributions in binary form must reproduce the
// *    above copyright notice, this list of conditions and the
// *    following disclaimer in the documentation and/or other
// *    materials provided with the distribution.
// *
// * 3. The name "jdbm" must not be used to endorse or promote
// *    products derived from this Software without prior written
// *    permission of Cees de Groot.  For written permission,
// *    please contact cg@cdegroot.com.
// *
// * 4. Products derived from this Software may not be called "jdbm"
// *    nor may "jdbm" appear in their names without prior written
// *    permission of Cees de Groot. 
// *
// * 5. Due credit should be given to the jdbm Project
// *    (http://jdbm.sourceforge.net/).
// *
// * THIS SOFTWARE IS PROVIDED BY THE ndbm PROJECT AND CONTRIBUTORS
// * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
// * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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// * CEES DE GROOT OR ANY CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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// * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
// * OF THE POSSIBILITY OF SUCH DAMAGE.
// *
// * Copyright 2000 (C) Cees de Groot. All Rights Reserved.
// * Contributions are Copyright (C) 2000 by their associated contributors.
// *
// * $Id: TranslationPage.java,v 1.1 2000/05/06 00:00:31 boisvert Exp $
// 

//*************************************************************************
//**  Included in JDMB 1.0 port to SharpDBM;  11/2013 Cyrus Neah cneah@codingreal.com
//**  SharpDBM is an independent reimplementation of the JDBM 1.0 software library in C#  
//*************************************************************************

namespace SharpDBM.recman
{

///
// *  Class describing a page that holds translations from physical rowids
// *  to logical rowids. In fact, the page just holds physical rowids - the
// *  page's block is the block for the logical rowid, the offset serve
// *  as offset for the rowids.
// 
	internal   class TranslationPage : PageHeader
	{
	// offsets
		internal const short O_TRANS = PageHeader.SIZE; // short count
		internal const short ELEMS_PER_PAGE = (RecordFile.BLOCK_SIZE - O_TRANS) / PhysicalRowId.SIZE;

	// slots we returned.
		internal readonly PhysicalRowId[] slots = new PhysicalRowId[ELEMS_PER_PAGE];

//    *
//     *  Constructs a data page view from the indicated block.
//     
		internal TranslationPage(BlockIo block) : base(block)
		{
		}

//    *
//     *  Factory method to create or return a data page for the
//     *  indicated block.
//     
		public static TranslationPage getTranslationPageView(BlockIo block)
		{
			BlockView view = block.getView();
			if (view != null && view is TranslationPage)
				return (TranslationPage) view;
			else
				return new TranslationPage(block);
		}

	/// Returns the value of the indicated rowid on the page 
		internal virtual PhysicalRowId @get(short offset)
		{
			int slot = (offset - O_TRANS) / PhysicalRowId.SIZE;
			if (slots[slot] == null)
				slots[slot] = new PhysicalRowId(block, offset);
			return slots[slot];
		}
	}

}